The present invention relates to certain novel pyrimidinone compounds, processes for their preparation, intermediates useful in their preparation, pharmaceutical compositions containing them and their use in therapy, in particular in the treatment of atherosclerosis.
WO 95/00649 (SmithKline Beecham plc) describe the phospholipase A2 enzyme Lipoprotein Associated Phospholipase A2 (Lp-PLA2), the sequence, isolation and purification thereof, isolated nucleic acids encoding the enzyme, and recombinant host cells transformed with DNA encoding the enzyme. Suggested therapeutic uses for inhibitors of the enzyme included atherosclerosis, diabetes, rheumatoid arthritis, stroke, myocardial infarction, reperfusion injury and acute and chronic inflammation. A subsequent publication from the same group further describes this enzyme (Tew D et al, Arterioscier Thromb Vas Biol 1996: 16;591-9) wherein it is referred to as LDL-PLA2. A later patent application (WO 95/09921, Icos Corporation) and a related publication in Nature (Tjoelker et al, vol 374, Apr. 6, 1995, 549) describe the enzyme PAF-AH which has essentially the same sequence as Lp-PLA2 and suggest that it may have potential as a therapeutic protein for regulating pathological inflammatory events.
It has been shown that Lp-PLA2 is responsible for the conversion of phosphatidylcholine to lysophosphatidylcholine, during the conversion of low density lipoprotein (LDL) to its oxidised form. The enzyme is known to hydrolyse the sn-2 ester of the oxidised phosphatidylcholine to give lysophosphatidylcholine and an oxidatively modified fatty acid. Both products of Lp-PLA2 action are biologically active with lysophosphatidylcholine, a component of oxidised LDL, known to be a potent chemoattractant for circulating monocytes. As such, lysophosphatidylcholine is thought play a significant role in atherosclerosis by being responsible for the accumulation of cells loaded with cholesterol ester in the arteries. Inhibition of the Lp-PLA2 enzyme would therefore be expected to stop the build up of these macrophage enriched lesions (by inhibition of the formation of lysophosphatidylcholine and oxidised free fatty acids) and so be useful in the treatment of atherosclerosis.
The increased lysophosphatidylcholine content of oxidatively modified LDL is also thought to be responsible for the endothelial dysfunction observed in patients with atherosclerosis. Inhibitors of Lp-PLA2 could therefore prove beneficial in the treatment of this phenomenon. An Lp-PLA2 inhibitor could also find utility in other disease states that exhibit endothelial dysfunction including diabetes, hypertension, angina pectoris and after ischaemia and reperfusion.
In addition, Lp-PLA2 inhibitors may also have a general application in any disorder that involves activated monocytes, macrophages or lymphocytes, as all of these cell types express Lp-PLA2. Examples of such disorders include psoriasis.
Furthermore, Lp-PLA2 inhibitors may also have a general application in any disorder that involves lipid peroxidation in conjunction with Lp-PLA2 activity to produce the two injurious products, lysophosphatidylcholine and oxidatively modified fatty acids. Such conditions include the aforementioned conditions atherosclerosis, diabetes, rheumatoid arthritis, stroke, myocardial infarction, reperfusion injury and acute and chronic inflammation. Further such conditions include various neuropsychiatric disorders such as schizophrenia (see Psychopharmacology Bulletin, 31, 159-165, 1995).
Patent applications WO 96/12963, WO 96/13484, WO96/19451, WO 97/02242, WO97/217675, WO97/217676, WO 96/41098, and WO97/41099 (SmithKline Beecham plc) disclose inter alia various series of 4-thionyl/sulfinyl/sulfonyl azetidinone compounds which are inhibitors of the enzyme Lp-PLA2. These are irreversible, acylating inhibitors (Tew et al, Biochemistry, 37, 10087, 1998).
WO 99/24420 (SmithKline Beecham) describes a new class of compounds which are inhibitors of Lp-PLA2, namely a group of pyrimidone compounds. We have now identified a particular subset of pyrimidone compounds which have a 5-(2-oxopyrimid-5-ylmethyl) substituent and which are potent inhibitors of Lp-PLA2 
Accordingly, the present invention provides a compound of the formula (I): 
in which:
R1 is COOH or a salt thereof, COOR10, CONR11R12, CN or CH2OH;
R2 is a mono- or bicyclic aromatic ring system containing up to 10 carbon atoms in the ring system, or a mono- or bicyclic heteroaromatic ring system including up to 4 heteroatoms selected from N, O and S; optionally substituted by 1, 2, 3 or 4 substituents selected from C1-4alkyl, C1-4alkoxy, C1-4alkylthio, aryl, aralkyl, hydroxy, oxo, halogen, CN, COOH or a salt thereof, COOxe2x80x94C1-6alkyl, CONR15R16, NR15COR16, SO2NR15R16, NR15SO2R16, NR15R16, mono to perfluoro C1-4alkyl and mono to perfluoro C1-4alkoxy;
R3 is C1-20 alkyl, C3-6 cycloalkyl, C3-6cycloalkylC1-5alkyl, or C1-10 alkoxyC1-10alkyl, each optionally substituted by 1 or 2 substituents selected from hydroxy, C1-10 alkoxy, COOH or a salt thereof, COOC1-15 alkyl, CONR17R18, NR17R18, NR17COR18, NR19 or an aromatic or heteroaromatic ring system as defined for R2, or R3 is an aromatic or heteroaromatic ring system as hereinbefore defined for R2;
R10 is C1-4alkyl or a pharmaceutically acceptable in vivo hydrolysable ester group;
R11 and R12 which may be the same or different is each selected from hydrogen, C1-12alkyl, CH2R13, CHR14CO2H or a salt thereof, or R11 and R12 together with the nitrogen to which they are attached form a 5- to 7 membered ring optionally containing one or more further heteroatoms selected from oxygen, nitrogen and sulphur, and optionally substituted by one or two substituents selected from hydroxy, oxo, C1-4alkyl, C1-4alkylCO, aryl, e.g. phenyl, or aralkyl, e.g benzyl, for instance morpholine or piperazine;
R13 is COOH or a salt thereof, COOR10, CONR11R12, CN or CH2OH;
R14 is an amino acid side chain such as CH2OH from serine;
R15 and R16 are independently hydrogen or C1-4 alkyl e.g. methyl or ethyl;
R17 and R18 are independently hydrogen, C1-15 alkyl, eg methyl or ethyl, C1-10 alkoxyC1-10 alkyl or arylC1-10 alkyl, e.g. benzyl;
R19 together with the nitrogen atom to which it is attached forms a 5- to 7 membered ring optionally containing one or more further heteroatoms selected from oxygen, nitrogen and sulphur, and optionally substituted by one or two substituents selected from hydroxy, oxo, C1-4 alkyl, aryl, e.g. phenyl, or aralkyl, e.g benzyl;
W is SO2 or a bond;
X is O or S; and
Y is a group of the formula xe2x80x94A1xe2x80x94A2xe2x80x94A3xe2x80x94 in which A1 and A3 each represent a bond or a straight chain or branched alkylene group, said alkylene group(s) containing a total of 1 to 10 carbon atoms and A2 represents a bond or O, S, SO, SO2, CO, Cxe2x95x90CH2, CONH, NHCO, CR15R16, CHxe2x95x90CH or Cxe2x89xa1C, providing that when A2 is O, S, SO, SO2or CONH, A3 contains at least two carbon atoms linking the A2 group and the CH2 group in formula (I).
Representative examples of R1 include carboxy (COOH) and corresponding salts, esters (COOR10) and amides (CONR11R12) thereof, for instance a sodium salt, an ethyl ester or an amide comprising an N-alkyl substituent, for instance, methyl, 2-methoxyethyl, octyl, dodecyl, N-benzyl, N-naphthylmethyl or a disubstitued amide comprising a combination thereof, or an amide in which the N forms part of a heterocyclic ring, for instance a piperidine ring.
Representative examples of the aromatic ring system represented by R2 include phenyl and naphthyl. Representative examples of the heteroaromatic ring system which may be represented by R2 include pyridyl, pyrimidinyl, pyrazolyl, furanyl, thienyl, thiazolyl, quinolyl, benzothiazolyl, pyridazolyl and pyrazinyl. Representative examples of R2 include the phenyl group optionally substituted by 1, 2 or 3 substituents selected from halogen (e.g. chlorine or fluorine), C1-4 alkyl (e.g. methyl or ethyl) or C1-4 alkoxy (e.g. methoxy), for instance 4-fluorophenyl. Examples of the aryl and aralkyl substituents in the R2 group include respectively phenyl and benzyl.
Representative examples of R3 include C1-20 alkyl, for instance methyl and undecyl, and R17R18NHCOCH2 in which R17 and R18 is each independently C1-15 alkyl, for instance R17 is methyl and R18 is methyl, octyl, or dodecyl.
Preferably, W is a bond.
Preferably, R3W is N-(1-Dodecyl)-N-methylaminocarbonylmethyl.
The group X is preferably S.
Preferred compounds of formula (I) include those in which Y is a bond, i.e. A1, A2 and A3 each representing a bond. Other preferred examples of the groups A1 and A3 are straight chain alkylene groups. When A2 is other than a bond, A1 is preferably a bond. Preferred examples of A2 above include CO, Cxe2x95x90CH2 and O, the CO group being especially preferred. Other preferred examples of Y are (CH2)7 or CO(CH2)6.
Pharmaceutically acceptable in vivo hydrolysable ester groups for R10 include those which break down readily in the human body to leave the parent acid or its salt.
Representative examples of values of pharmaceutically acceptable in vivo hydrolysable ester groups for R10 include:
xe2x80x94CH(Ra)O.CO.Rb;
xe2x80x94CH(Ra)O.CO.ORc;
xe2x80x94CH(Ra)CO.NReRf 
xe2x80x94RdNReRf;
xe2x80x94CH2ORg; 
xe2x80x83CH(Ra)O.CO.C6H4Y1COCH(Ri)NH2; and 
in which:
Ra is hydrogen, (C1-6)alkyl, in particular methyl, (C3-7)cycloalkyl, or phenyl, each of which may be optionally substituted;
Rb is (C1-6)alkyl, (C1-6)alkoxy(C1-6)alkyl, phenyl, benzyl, (C3-7)cycloalkyl, (C1-6)alkyl(C3-7)cycloalkyl, 1-amino(C1-6)alkyl, or 1-(C1-6alkyl)amino(C1-6)alkyl, each of which may be optionally substituted; or
Ra and Rb together form a 1,2-phenylene group optionally substituted by one or two methoxy groups;
Rc is (C1-6)alkyl, (C3-7)cycloalkyl, (C1-6)alkyl(C3-7)cycloalkyl;
Rd is (C1-6)alkylene optionally substituted with a methyl or ethyl group;
Re and Rf which may be the same or different is each (C1-6)alkyl; or aryl(C1-4)alkyl, optionally substituted with e.g. hydroxy;
Rg is (C1-6)alkyl;
Rh is hydrogen, (C1-6)alkyl or phenyl;
Ri is hydrogen or phenyl optionally substituted by up to three groups selected from halogen, (C1-6)-alkyl, or (C1-6)alkoxy; and
Y1 is oxygen or NH;
for instance:
(a) acyloxyalkyl groups such as acetoxymethyl, isobutyryloxymethyl, pivaloyloxymethyl, benzoyloxymethyl, xcex1-acetoxyethyl, xcex1-pivaloyloxyethyl, 1-(cyclohexylcarbonyloxy)ethyl, (1-aminoethyl)carbonyloxymethyl, 2-methoxyprop-2-ylcarbonyloxymethyl, phenylcarbonyloxymethyl and 4-methoxyphenyl-carbonyloxymethyl;
(b) alkoxy/cycloalkoxycarbonyloxyalkyl groups, such as ethoxycarbonyloxymethyl, t-butyloxycarbonyloxymethyl, cyclohexyloxycarbonyloxymethyl, 1-methylcyclohexyloxycarbonyloxymethyl and xcex1-ethoxycarbonyloxyethyl;
(c) dialkylaminoalkanol, especially di-loweralkylamino alkyl groups such as dimethylaminomethyl, dimethylaminoethyl, dimethylaminomethyl or diethylaminoethyl;
(d) acetamido groups such as N,N-dimethylaminocarbonylmethyl, N,N-(2-hydroxyethyl)aminocarbonylmethyl;
(e) lactone groups such as phthalidyl and dimethoxyphthalidyl;
(f) (5-methyl-2-oxo-1,3-dioxolen-4-yl)methyl; and
(g) (2-methoxycarbonyl-E-but-2-en-yl)methyl.
Representative examples of pharmaceutically acceptable in vivo hydrolysable ester groups for R10 include:
(2-methoxycarbonyl-E-but-2-en-yl)methyl, isobutyryloxymethyl, 2-methoxyprop-2-ylcarbonyloxymethyl, phenylcarbonyloxymethyl, 4-methoxyphenyl-carbonyloxymethyl, t-butyloxycarbonyloxymethyl, cyclohexyloxy-carbonyloxymethyl, 1-methylcyclohexyloxycarbonyloxymethyl, N,N-dimethylaminocarbonylmethyl, and (5-methyl-2-oxo-1,3-dioxolen-4-yl)methyl.
When used herein, the term xe2x80x9calkylxe2x80x9d and similar terms such as xe2x80x9calkoxyxe2x80x9d include all straight chain and branched isomers.
It will be appreciated that in some instances, compounds of the present invention may include a carboxy group as a substituent. Such carboxy groups may be used to form salts, in particular pharmaceutically acceptable salts. Pharmaceutically acceptable salts include those described by Berge, Bighley, and Monkhouse, J. Pharm. Sci., 1977, 66, 1-19. Preferred salts include alkali metal salts such as the sodium and potassium salts.
Compounds of formula (I) are inhibitors of Lp-PLA2 and as such are expected to be of use in treating atherosclerosis and the other disease conditions noted elsewhere. Such compounds are found to act as inhibitors of Lp-PLA2 in in vitro assays.
Particularly preferred compounds of formula (I) include:
1-(N-(1-Octyl)-N-methylaminocarbonylmethyl)-2-(4-fluorobenzyl)thio-5-(1-carboxymethyl-2-oxopyrimid-5-ylmethyl)pyrimidin-4-one;
1-(N-(1-Octyl)-N-methylaminocarbonylmethyl)-2-(4-fluorobenzyl)thio-5-(1-(methylaminocarbonylmethyl)-2-oxopyrimid-5-ylmethyl)pyrimidin-4-one;
1-(N-(1-Dodecyl)-N-methylaminocarbonylmethyl)-2-(4-fluorobenzyl)thio-5-(1-(methylaminocarbonylmethyl)-2-oxopyrimid-5-ylmethyl)pyrmidin-4-one;
1-(N-(1-Dodecyl)-N-methylaminocarbonylmethyl)-2-(4-fluorobenzyl)thio-5-(1-(1-morpholinocarbonylmethyl)-2-oxopyrimid-5-ylmethyl)pyrimidin-4-one; and
1-(N-(1-Dodecyl)-N-methylaminocarbonylmethyl)-2-(4-fluorobenzyl)thio-5-(1-carboxymethyl-2-oxopyrimid-5-ylmethyl)pyrimidin-4-one and the sodium salt thereof.
Since the compounds of the present invention, in particular compounds of formula (I), are intended for use in pharmaceutical compositions, it will be understood that they are each provided in substantially pure form, for example at least 50% pure, more suitably at least 75% pure and preferably at least 95% pure (% are on a wt/wt basis). Impure preparations of the compounds of formula (I) may be used for preparing the more pure forms used in the pharmaceutical compositions. Although the purity of intermediate compounds of the present invention is less critical, it will be readily understood that the substantially pure form is preferred as for the compounds of formula (I). Preferably, whenever possible, the compounds of the present invention are obtained in crystalline form.
When some of the compounds of this invention are allowed to crystallise or are recrystallised from organic solvents, solvent of crystallisation may be present in the crystalline product. This invention includes within its scope such solvates. Similarly, some of the compounds of this invention may be crystallised or recrystallised from solvents containing water. In such cases water of hydration may be formed. This invention includes within its scope stoichiometric hydrates as well as compounds containing variable amounts of water that may be produced by processes such as lyophilisation. In addition, different crystallisation conditions may lead to the formation of different polymorphic forms of crystalline products. This invention includes within its scope all polymorphic forms of the compounds of formula (I).
Compounds of the present invention are inhibitors of the enzyme lipoprotein associated phospholipase A2 (Lp-PLA2) and as such are expected to be of use in therapy, in particular in the treatment of atherosclerosis. In a further aspect therefore the present invention provides a compound of formula (I) for use in therapy.
The compounds of formula (I) are inhibitors of lysophosphatidylcholine production by Lp-PLA2 and may therefore also have a general application in any disorder that involves endothelial dysfunction, for example atherosclerosis, diabetes, hypertension, angina pectoris and after ischaemia and reperfusion. In addition, compounds of formula (I) may have a general application in any disorder that involves lipid peroxidation in conjunction with enzyme activity, for example in addition to conditions such as atherosclerosis and diabetes, other conditions such as rheumatoid arthritis, stroke, inflammatory conditions of the brain such as Alzheimer""s Disease, myocardial infarction, reperfusion injury, sepsis, and acute and chronic inflammation. Further such conditions include various neuropsychiatric disorders such as schizophrenia (see Psychopharmacology Bulletin, 31, 159-165, 1995).
Further applications include any disorder that involves activated monocytes, macrophages or lymphocytes, as all of these cell types express Lp-PLA2. Examples of such disorders include psoriasis.
Accordingly, in a further aspect, the present invention provides for a method of treating a disease state associated with activity of the enzyme Lp-PLA2 which method involves treating a patient in need thereof with a therapeutically effective amount of an inhibitor of the enzyme. The disease state may be associated with the increased involvement of monocytes, macrophages or lymphocytes; with the formation of lysophosphatidylcholine and oxidised free fatty acids; with lipid peroxidation in conjunction with Lp PLA2 activity; or with endothelial dysfunction.
Compounds of the present invention may also be of use in treating the above mentioned disease states in combination with anti-hyperlipidaemic or anti-atherosclerotic or anti-diabetic or anti-anginal or anti-inflammatory or anti-hypertension agents. Examples of the above include cholesterol synthesis inhibitors such as statins, anti-oxidants such as probucol, insulin sensitisers, calcium channel antagonists, and anti-inflammatory drugs such as NSAIDs.
In therapeutic use, the compounds of the present invention are usually administered in a standard pharmaceutical composition. The present invention therefore provides, in a further aspect, a pharmaceutical composition comprising a compound of formula (I) and a pharmaceutically acceptable carrier.
Suitable pharmaceutical compositions include those which are adapted for oral or parenteral administration or as a suppository. Compounds of formula (I) which are active when given orally can be formulated as liquids, for example syrups, suspensions or emulsions, tablets, capsules and lozenges. A liquid formulation will generally consist of a suspension or solution of the compound or pharmaceutically acceptable salt in a suitable liquid carrier(s) for example, ethanol, glycerine, non-aqueous solvent, for example polyethylene glycol, oils, or water with a suspending agent, preservative, flavouring or colouring agent. A composition in the form of a tablet can be prepared using any suitable pharmaceutical carrier(s) routinely used for preparing solid formulations. Examples of such carriers include magnesium stearate, starch, lactose, sucrose and cellulose. A composition in the form of a capsule can be prepared using routine encapsulation procedures. For example, pellets containing the active ingredient can be prepared using standard carriers and then filled into a hard gelatin capsule; alternatively, a dispersion or suspension can be prepared using any suitable pharmaceutical carrier(s), for example aqueous gums, celluloses, silicates or oils and the dispersion or suspension then filled into a soft gelatin capsule. Typical parenteral compositions consist of a solution or suspension of the compound of formula (I) in a sterile aqueous carrier or parenterally acceptable oil, for example polyethylene glycol, polyvinyl pyrrolidone, lecithin, arachis oil or sesame oil. Alternatively, the solution can be lyophilised and then reconstituted with a suitable solvent just prior to administration. A typical suppository formulation comprises a compound of formula (I) which is active when administered in this way, with a binding and/or lubricating agent such as polymeric glycols, gelatins or cocoa butter or other low melting vegetable or synthetic waxes or fats.
Preferably the composition is in unit dose form such as a tablet or capsule. Each dosage unit for oral administration contains preferably from 1 to 500 mg (and for parenteral administration contains preferably from 0.1 to 25 mg) of a compound of the formula (I). The daily dosage regimen for an adult patient may be, for example, an oral dose of between 1 mg and 1000 mg, preferably between 1 mg and 500 mg, or an intravenous, subcutaneous, or intramuscular dose of between 0.1 mg and 100 mg, preferably between 0.1 mg and 25 mg, of the compound of the formula (I), the compound being administered 1 to 4 times per day. Suitably the compounds will be administered for a period of continuous therapy, for example for a week or more.
Compounds of formula (I) may be conveniently prepared by a process which comprises reacting a compound of formula (II): 
in which
R2, R3, W, X and Y are as hereinbefore defined;
with an alkylating agent of formula R1xe2x80x94CH2xe2x80x94L1 in which R1 is as hereinbefore defined and L1 is a leaving group such as chloride, bromide, iodide or mesylate, in the presence of a base such as potassium carbonate; and thereafter, and if necessary,
interconverting groups in R1, for example COOR10 to COOH by standard conditions (alkaline hydrolysis, hydrogenation of benzyl ester, etc), or COOH to CONR11R12 by amide coupling.
A compound of formula (II) can conveniently by prepared by O-dealkylation of the corresponding compound of formula (III): 
in which
R20 is C1-4 alkyl, arylmethyl or diarylmethyl and R2, R3, W, X and Y are as hereinbefore defined. Typical conditions include treatment with boron tribromide or B-bromocatecholborane in dichloromethane at temperatures between xe2x88x9220xc2x0 and ambient;
hydrogenolysis of benzyloxy groups; acid cleavage of O-tBu.
A compound of formula (III) may be readily prepared in a series of steps from a compound of formula (IV): 
in which
R21 is hydrogen or C1-4alkyl, for instance methyl or ethyl, R22 is hydrogen or methyl and R20 is as hereinbefore defined;
using procedures well known in the art for thiouracil formation, N-alkylation and thioetherification.
Thus, for instance, for a compound of formula (III) in which W is a bond, a compound of formula (IV) in which R21 is hydrogen and R22 is methyl may be treated with oxalyl chloride in a dry solvent such as dichloroethane, to form an intermediate acyl chloride, followed by treatment with potassium thiocyanate in the presence of a solvent such as acetonitrile, and then treatment with a compound of the formula (V):
R3WNH2xe2x80x83xe2x80x83(V)
in which W is a bond and R3 is as hereinbefore defined; followed by the addition of a base such as sodium ethoxide, to give a thiouracil compound of the formula (VI): 
in which R3, R20 and W are as hereinbefore defined. The compound of formula (VI) may then be treated with a compound of the formula (VII):
R2YCH2L1xe2x80x83xe2x80x83(VII)
in which L1 and R2 are as hereinbefore defined; to give a compound of formula (III) in which X is S.
In an alternative approach, a compound of formula (IV) in which R21 is C1-4alkyl, for instance methyl, and R22 is methyl, may be treated with thiourea, to form a thiouracil of the formula (VIII): 
in which R20 is a hereinbefore defined. This thiouracil may then be treated with a compound of the formula (VII) as hereinbefore described, to give a compound of formula (IX): 
in which R2, R20 and Y are as hereinbefore defined and X is S. Subsequent reaction of a compound of formula (IX) with a compound of the formula (X):
R3WL1xe2x80x83xe2x80x83(X)
in which L1, R3 and W are as hereinbefore defined; leads to a compound of formula (III) in which X is S.
Compounds of formula (IV) may be readily obtained from a convenient, readily available pyrimdine starting material such as a 2-alkoxy 5-bromopyrimidine, using processes well known in the art. This pyrimidine may be coupled with an acrylate ester such as ethyl or methyl acrylate, using a Heck reaction, and the intermediate then subjected to catalytic hydrogenation to give a propionic acid ester derivative. This in turn may be treated with methyl formate in the presence of a strong base such as potassium t-butoxide or sodium hydride, to give a compound of formula (IV) in which R22 is hydrogen. Alkylation, for instance methylation, using dimethyl sulphate, then gives a compound of formula (IV) in which R22 is alkyl. A compound of formula (IV) in which R21 is hydrogen (ie the carboxylic acid) may be obtained from the corresponding ester by hydrolysis under basic conditions, for instance aqueous sodium hydroxide.
Compounds of formula (I) in which X is O may be conveniently be prepared from corresponding compounds of formula (I) in which X is S by treatment thereof with a compound of the formula (XI):
R2YCH2OHxe2x80x83xe2x80x83(XI)
in which R2 is as hereinbefore defined.